Record receiver having plural interactive leaves or a colorless – Having a colorless color-former – developer therefor – or... – Having constituent defined in terms of melting temperature
Patent
1992-05-26
1994-03-22
Schwartz, Pamela R.
Record receiver having plural interactive leaves or a colorless
Having a colorless color-former, developer therefor, or...
Having constituent defined in terms of melting temperature
503209, 503225, B41M 530
Patent
active
052964400
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to heat-sensitive recording media and, more particularly, to heat-sensitive recording media excellent in storage stability of record images.
BACKGROUND ART
Heat-sensitive recording media are well known in the art which make use of the reaction between a colorless or pale-colored basic dye and a color developing material and give images upon application of heat which brings the color developing material into contact with the basic dye. Such heat-sensitive recording media have the drawback that record images generally have insufficient storage stability and become faded with the lapse of time. Particularly when heat-sensitive recording media are stored under high humidity and/or high temperature conditions, record images may fade away in a relatively short period of time. Improvement in this respect is earnestly desired.
For improving the storage stability of record images, various heat-sensitive recording media containing a storage stability improving agent or agents have been proposed. However, the improvement in storage stability is generally compromised by newly accompanying drawbacks such as reduced whiteness and adhesion of residual substances to the thermal head. Thus, the results are not invariably satisfactory.
DISCLOSURE OF THE INVENTION
With the above situation in view, the present inventors conducted intensive investigations on storage stability improving agents to be contained in the recording layer. As a result, we found that 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate, an alkali metal salt thereof, an ammonium salt thereof, polyvalent metal salt thereof, or a mixture of these, when contained, in the recording layer, give heat-sensitive recording media excellent in storage stability of record images without accompanying any new drawback. The present invention has now been completed based on this finding.
The present invention thus provides a heat-sensitive recording medium comprising
(a) a support and
(b) a heat-sensitive recording layer formed on the support and comprising a colorless or pale-colored basic dye and a color developing material capable of causing color development upon contact with the dye by heating, which medium is characterized in that said heat-sensitive recording layer contains at least one phosphate compound selected from the group consisting of 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate of the general formula (1) shown below and alkali metal, ammonium and polyvalent metal salts thereof: ##STR2## wherein each R represents a tert-butyl group.
In an embodiment of the invention, the heat-sensitive recording layer contains at least one of 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate represented by the above general formula (1) and alkali metal and ammonium salts thereof.
In another embodiment of the invention, the above-mentioned heat-sensitive recording layer contains at least one of polyvalent metal salts of 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate.
The above-mentioned embodiments of the invention are described below in further detail.
EMBODIMENT (I)
In one embodiment of the invention, the heat-sensitive recording layer contains at least one phosphate compound selected from among 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate represented by the above general formula (1) and alkali metal and ammonium salts thereof. Preferably, the heat-sensitive recording layer mentioned above contains at least one of 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate and alkali metal salts thereof.
The heat-sensitive recording medium in this embodiment is excellent in storage stability of record images and, in addition, is resistant to fogging , thus generally featuring a high level of whiteness of the heat-sensitive recording layer.
As specific examples of the compound of the above general formula (1) and of alkali metal and ammonium salts thereof, there may be mentioned, for example, 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate, sodium salt of 2,2'-methylenebis(4,6-di-tert-butylphe
REFERENCES:
patent: 3937864 (1976-02-01), Kohmura et al.
patent: 4473831 (1984-09-01), Watanabe
patent: 4771033 (1988-09-01), Shimizu et al.
patent: 5175138 (1992-12-01), Akutsu et al.
Arai Naoto
Kanda Nobuo
Nakano Isamu
Okamoto Tosaku
Tsuchida Tetsuo
Kanzaki Paper Manufacturing Co. Ltd.
Schwartz Pamela R.
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